Magnesium-protoporphyrin IX monomethyl ester (oxidative) cyclase
April 12, 2024
Magnesium-protoporphyrin IX monomethyl ester (oxidative) cyclase (EC 1.14.13.81), is an enzyme with systematic namemagnesium-protoporphyrin-IX 13-monomethyl ester, ferredoxin:oxygen oxidoreductase (hydroxylating).[1] In plants this enzyme catalyses the following overall chemical reaction
Magnesium-protoporphyrin IX monomethyl ester (oxidative) cyclase
The chlorin ring system forms as the esterified propionate sidechain is cyclised on to the porphyrin ring of protoporphyrin IX to form divinylprotochlorophyllide
Recent evidence[2] shows that the necessary electrons which cycle the enzyme from oxidised to reduced form come from ferredoxin. In green tissue, ferredoxin can receive these electrons directly from photosystem I so that NADPH need not be involved. However, in the dark, ferredoxin can also be reduced via Ferredoxin—NADP(+) reductase, allowing the reaction to proceed in that case. It is therefore more accurate to show the individual steps as follows:
(1a) magnesium-protoporphyrin IX 13-monomethyl ester + 2 reduced ferredoxin + O2 131-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + H2O
(1b) 131-hydroxy-magnesium-protoporphyrin IX 13-monomethyl ester + 2 reduced ferredoxin + O2 131-oxo-magnesium-protoporphyrin IX 13-monomethyl ester + 2 H2O
This enzyme requires Fe(II) for activity. In barley the cyclase protein is named XanL and is encoded by the Xantha-l gene. An associated protein, Ycf54, seems to be required for proper maturation of the XanL enzyme,[2] which is part of the biosynthetic pathway to chlorophylls.[3][4][5] In anaerobic organisms such as Rhodobacter sphaeroides the same overall transformation occurs but the oxygen incorporated into magnesium-protoporphyrin IX 13-monomethyl ester comes from water in the reaction EC 1.21.98.3.[6]
^Tanaka, Ryouichi; Tanaka, Ayumi (2007). "Tetrapyrrole Biosynthesis in Higher Plants". Annual Review of Plant Biology. 58: 321–346. doi:10.1146/annurev.arplant.57.032905.105448. PMID 17227226.
^Porra, Robert J.; Schafer, Wolfram; Gad'On, Nasr; Katheder, Ingrid; Drews, Gerhart; Scheer, Hugo (1996). "Origin of the Two Carbonyl Oxygens of Bacteriochlorophyll a. Demonstration of two Different Pathways for the Formation of Ring e in Rhodobacter sphaeroides and Roseobacter denitrificans, and a Common Hydratase Mechanism for 3-acetyl Group Formation". European Journal of Biochemistry. 239 (1): 85–92. doi:10.1111/j.1432-1033.1996.0085u.x. PMID 8706723.
magnesium, protoporphyrin, monomethyl, ester, oxidative, cyclase, enzyme, with, systematic, name, magnesium, protoporphyrin, monomethyl, ester, ferredoxin, oxygen, oxidoreductase, hydroxylating, plants, this, enzyme, catalyses, following, overall, chemical, re. Magnesium protoporphyrin IX monomethyl ester oxidative cyclase EC 1 14 13 81 is an enzyme with systematic name magnesium protoporphyrin IX 13 monomethyl ester ferredoxin oxygen oxidoreductase hydroxylating 1 In plants this enzyme catalyses the following overall chemical reactionMagnesium protoporphyrin IX monomethyl ester oxidative cyclaseIdentifiersEC no 1 14 13 81CAS no 92353 62 3DatabasesIntEnzIntEnz viewBRENDABRENDA entryExPASyNiceZyme viewKEGGKEGG entryMetaCycmetabolic pathwayPRIAMprofilePDB structuresRCSB PDB PDBe PDBsumSearchPMCarticlesPubMedarticlesNCBIproteins The chlorin ring system forms as the esterified propionate sidechain is cyclised on to the porphyrin ring of protoporphyrin IX to form divinylprotochlorophyllidemagnesium protoporphyrin IX 13 monomethyl ester 3 NADPH 3 H 3 O2 displaystyle rightleftharpoons divinylprotochlorophyllide 3 NADP 5 H2O overall reaction Recent evidence 2 shows that the necessary electrons which cycle the enzyme from oxidised to reduced form come from ferredoxin In green tissue ferredoxin can receive these electrons directly from photosystem I so that NADPH need not be involved However in the dark ferredoxin can also be reduced via Ferredoxin NADP reductase allowing the reaction to proceed in that case It is therefore more accurate to show the individual steps as follows 1a magnesium protoporphyrin IX 13 monomethyl ester 2 reduced ferredoxin O2 displaystyle rightleftharpoons 131 hydroxy magnesium protoporphyrin IX 13 monomethyl ester H2O 1b 131 hydroxy magnesium protoporphyrin IX 13 monomethyl ester 2 reduced ferredoxin O2 displaystyle rightleftharpoons 131 oxo magnesium protoporphyrin IX 13 monomethyl ester 2 H2O 1c 131 oxo magnesium protoporphyrin IX 13 monomethyl ester 2 reduced ferredoxin O2 displaystyle rightleftharpoons divinylprotochlorophyllide 2 H2OThis enzyme requires Fe II for activity In barley the cyclase protein is named XanL and is encoded by the Xantha l gene An associated protein Ycf54 seems to be required for proper maturation of the XanL enzyme 2 which is part of the biosynthetic pathway to chlorophylls 3 4 5 In anaerobic organisms such as Rhodobacter sphaeroides the same overall transformation occurs but the oxygen incorporated into magnesium protoporphyrin IX 13 monomethyl ester comes from water in the reaction EC 1 21 98 3 6 See also editBiosynthesis of chlorophyllsReferences edit Bollivar DW Beale SI September 1996 The Chlorophyll Biosynthetic Enzyme Mg Protoporphyrin IX Monomethyl Ester Oxidative Cyclase Characterization and Partial Purification from Chlamydomonas reinhardtii and Synechocystis sp PCC 6803 Plant Physiology 112 1 105 114 doi 10 1104 pp 112 1 105 PMC 157929 PMID 12226378 a b Stuart D Sandstrom M Youssef HM Zakhrabekova S Jensen PE Bollivar DW Hansson M 2020 09 08 Aerobic Barley Mg protoporphyrin IX Monomethyl Ester Cyclase is Powered by Electrons from Ferredoxin Plants 9 9 1157 doi 10 3390 plants9091157 PMC 7570240 PMID 32911631 Willows RD June 2003 Biosynthesis of chlorophylls from protoporphyrin IX Natural Product Reports 20 3 327 41 doi 10 1039 B110549N PMID 12828371 Bollivar DW November 2006 Recent advances in chlorophyll biosynthesis Photosynthesis Research 90 2 173 94 doi 10 1007 s11120 006 9076 6 PMID 17370354 S2CID 23808539 Tanaka Ryouichi Tanaka Ayumi 2007 Tetrapyrrole Biosynthesis in Higher Plants Annual Review of Plant Biology 58 321 346 doi 10 1146 annurev arplant 57 032905 105448 PMID 17227226 Porra Robert J Schafer Wolfram Gad On Nasr Katheder Ingrid Drews Gerhart Scheer Hugo 1996 Origin of the Two Carbonyl Oxygens of Bacteriochlorophyll a Demonstration of two Different Pathways for the Formation of Ring e in Rhodobacter sphaeroides and Roseobacter denitrificans and a Common Hydratase Mechanism for 3 acetyl Group Formation European Journal of Biochemistry 239 1 85 92 doi 10 1111 j 1432 1033 1996 0085u x PMID 8706723 Portal nbsp Biology Retrieved from https en wikipedia org w index php title Magnesium protoporphyrin IX monomethyl ester oxidative cyclase amp oldid 1172352599, wikipedia, wiki, book, books, library,
